1. Field of the Invention
The invention generally relates to personal winter vehicles, and more specifically to a cycle that may be operated in snow and ice.
2. Description of Related Art
People frequently recreate in cold climates and in snowy conditions. In several types of recreational activities that take place in snowy or icy conditions, the individual rides up a mountain on a mechanical conveyance and then, at the summit of the mountain, slides down the snowy slopes of the mountain. Such activities include skiing, snowboarding, telemarking, and the like. In these types of activities, flat or uphill portions of the mountain reduce one's rate of travel and generally one's enjoyment of the activity. If one stops on a flat or uphill portion of the mountain, building up the momentum to overcome gravity and friction and begin travelling again (and especially to remain travelling) can be an arduous task. Cross-country skis are designed to allow a person to travel on flat portions of land, however they are not ideal for downhill portions of land. Similarly, downhill skis are typically only useful for travelling downhill and are less than desirable for flat portions of land.
People also like to recreate on bicycles. Some individuals have combined typical cold weather activities such as skiing and conventional bicycling in developing a "snow bike." Examples of snow bikes are found in U.S. Pat. No. 2,633,365 to Cwynar et al., U.S. Pat. No. 3,561,783 to Ellett, U.S. Pat. No. 4,027,891 to Frame, and U.S. Pat. No. 4,059,168 to House, the teachings of which are herein incorporated by reference.
The Ellett and Frame devices are essentially bicycle frames with the wheels replaced with short skis. Neither provides any ability for a user to use force to propel the vehicle. The Ellett and Frame devices are limited to use on downhill slopes. Three companies, Brenter, Ludwig, and Vertex, currently market snow bikes of this nature. The user is intended to wear short skis on his or her feet while operating the snow bike for stability.
The Cwynar device is described as a "ski scooter" and is intended to be used by a standing individual. The user keeps one foot on the running board and pushes off the ground with the other foot in a manner similar to propelling a conventional scooter. Instead of wheels, the Cwynar device includes runners, one in the front and two in the rear. The use of one's foot to propel a wheeled scooter on ordinary ground is difficult enough; however, additional problems arise when using such a device on snow or ice. For example, the coefficient of friction between a person's foot and snow/ice is substantially smaller than that between a person's foot and a paved road; one could easily slip when trying to propel the device. Also, on snow that is not uniformly packed down, a person may step into a patch of snow that is deeper and more loosely packed than the person expected, resulting in the person losing his balance and falling from the scooter.
The House device converts a standard bicycle frame by adding skis and a fan on the rear of the frame. The motor-driven fan is intended to create sufficient thrust to propel a person across a snowy field. Because the pedals of the bicycle frame are no longer attached to any resistance-providing structure, a user cannot obtain much exercise benefit from use of this device.
Another device that enables a person to propel a personal vehicle over snow/ice was described in U.S. Pat. No. 551,442 to Korff, the teachings of which are herein incorporated by reference. Korff modified a standard bicycle frame by replacing the front wheel with a guide runner and by adding a rear runner behind it. The rear wheel was left in place and stud plates were placed around the circumference thereof. A user would pedal the device thus causing the rear wheel to turn. Because the wheel was provided with studs for better traction, and because the runners exhibit reduced coefficient of friction, the device would be propelled across snow/ice. However, even with the studs on the wheel, such a device will slip on ice because only a small portion of the wheel tread is in contact with the ice at any given moment. Moreover, no braking mechanism is provided.
All of the above devices suffer from several deficiencies. The Ellett and Frame devices do not allow a user any ability to use force to propel the vehicle. The Cwynar device is difficult to operate and unreliable owing to the non-uniform nature of snow and ice. The House device does not afford an individual any significant exercise. Moreover, much like a conventional snowmobile, the fan required to propel an average weight person is likely to be enormous, heavy, loud, and impractical. Further, none of the above-mentioned devices allow the user to brake or reduce speed in any safe manner. The user must also, in each device listed above, use the respective devices in a single mode only; no provision is made for increasing the mechanical advantage a person has for an inclined surface and/or decreasing the mechanical advantage when riding on downhill slopes. The prior devices also fail to teach a device capable of switching between a motorized or motor-assisted mode of operation and a manual mode. Also, none of the devices mentioned above are suitable for extremely arduous or difficult maneuvering at high speeds, in what is commonly referred to as "extreme sporting" events.